The use of portable or hand-held electrical equipment in harsh outdoor environments and in particular by soldiers in combat environments is becoming commonplace. It is desirable and sometimes essential that such equipment be repeatedly connected and disconnected to a power supply and/or other electrical equipment so that the equipment can perform its function and be stowed when not in use.
Electrical connectors currently used in combat environments employ direct electrical contacts and a sealing mechanism to protect the connector. Typically, the sealed connectors are circular and use a threaded connection. Examples of these sorts of connectors are MIL-STD-1760 and MIL-STD-38999 connectors.
In contrast to these direct contact connectors, the present invention relates to contact-less connectors, and in particular inductively coupled connectors, and so some discussion of this type of technology is useful.
In an inductive connector there is no direct transfer of electrical energy from one connector part to the other. Instead the electrical energy is inductively coupled from one connector part to the other in the same manner as in a transformer. Similarly, in a capacitive connector, electrical energy is transferred from one connector to the other across a dielectric in the same manner as in a capacitor.
The principal of contact-less or indirect electromagnetic coupling has been employed to transfer electrical power between electric vehicles and charging stations (WO98/31073) and between under water electrical cables (U.S. Pat. No. 4,538,863 and GB2,136,635).
These connectors employ pairs of inductors, one in each half of the connector, each having a conductive winding around a ferromagnetic core. The inductors are located at the end of respective halves of the connector such that when connected the two halves of the connector are in face to face orientation to produce end-on mating of the two inductors.
The two parts of the connectors are generally held securely together by bolts, screw threads or even hydraulic actuators, thereby ensuring a tight fit and reliable long term connection.
An inductive connector has also been used to transmit measurement signals from a transmission line to a sensor and again an end-on orientation is disclosed (US2002/0102884).
The provision of electrical connectors suitable for use in harsh outdoor environments as part of equipment that is to be carried or worn by an individual and in particular by soldiers in a combat environment is becoming increasingly important. As noted above, this is because the use of electrical equipment by, for example, soldiers and other military personnel is becoming increasingly commonplace. Connectors used in these environments must be robust enough to stand up to the rigours of the outdoor environment whilst being light and small enough so as not to impede the mobility of the individual. In addition the electrical connection made by the connector must be reliable and accurate so that the electrical equipment in question can perform its function.
The inventors of the present invention have realised that conventional direct contact electrical connectors have a number of drawbacks when employed in environments such as those experienced by military personnel in training and in combat.
Firstly, repeated opening and closing of any direct contact electrical connector will inevitably involve wear and tear of the contact surfaces, especially if significant power is passing through the connector at the time the connector is disconnected since this may cause arcing and oxidation at the contact surface. This results in degraded performance over time and can reduce the lifespan of the connector and/or equipment and increase maintenance costs.
Secondly, when electrical connectors are opened and closed in these environments there will inevitably be some dirt, dust or liquid that contaminates one or both halves of the connector. In a simple direct contact conductive connector, any dust or dirt on the contact surfaces will reduce the efficiency of the electrical connection with the result that the equipment may function incorrectly, inefficiently or not at all. Conventional connectors do not cope well in the environments experienced by soldiers, in particular immersion in salt water, the ingress of sand and exposure to chemical warfare agents.